The present invention relates to a preparation method for a radiographic image conversion panel using a photostimulable phosphor and a radiographic image conversion panel prepared by the method.
Radiographic images, such as X-ray images, are widely used for disease diagnosis and other purposes.
Recently, U.S. Pat. No. 3,859,527 and Japanese Patent O.P.I. Publication No. 12144/1980 each disclose a method of radiographic image conversion using a photostimulable phosphor in the presence of visible light or infrared rays as stimulating excitation light. These methods use a radiographic image conversion panel comprising a support and a layer of photostimulable phosphor formed thereon. The layer of photostimulable phosphor of this radiographic image conversion panel is irradiated with radioactive rays that passed through the subject to accumulate radiation energy according to the radiation permeability of each portion of the subject for forming a latent image (cumulative image); the layer of photostimulable phosphor is then scanned with stimulating excitation light to cause it radiate the radiation energy accumulated in each portion and convert it to light; an image is obtained on the basis of the light signal corresponding to the intensity of this light. The eventual image thus obtained may be reproduced as a hard copy or on CRT.
The radiographic image conversion panel having a layer of photostimulable phosphor, used for this method of radiographic image conversion, needs to produce images of good graininess and high sharpness, as well as to have high percent absorption of radiation and high photoconversion efficiency (hereinafter together referred to as "radiation sensitivity") similarly in the radiography using the conventions fluorescent screen.
Recently a conversion panel containing no binding agent was developed. Thought this panel is advantageous because it has high packing density of phosphor and therefore has a satisfactory sensitivity with a thin phosphor layer, there is certain room to improve image sharpness. The sharpness depends on the directional characteristics of the stimulating excitation light introduced into the phosphor layer.
In the light of this drawback, the following methods have recently been proposed one by one with the aim of improving image sharpness:
(1) The method in which, as shown in FIG. 10, fine prismatic blocks 94 are prepared by depositing a photostimulable phosphor 93 on a support 92 having a fine rugged pattern (tiles etc.) 91 to form gaps 95 among the prismatic blocks 94 (Japanese Patent O.P.I. Publication No. 142497/1986).
(2) The method in which, as shown in FIG. 11, gaps 105 formed among blocks 104 obtained by depositing a photostimulable phosphor 103 on a support 102 having a fine rugged pattern 101 are grown by shock treatment (Japanese Patent O.P.I. Publication No. 142500/1986). Note that 106 is a protective layer.
(3) The method in which, as shown in FIG. 12, gaps 113 are formed in a layer of photostimulable phosphor 112 deposited on the upper surface of a support 111 from the upper face of the layer of the phosphor (Japanese Patent O.P.I. Publication No. 39797/1987). Note that 114 is a protective layer.
(4) The method in which, as shown in FIG. 13, a layer of photostimulable phosphor 123 having hollows 122 is formed on the upper surface of a support 121 by atmospheric vapor deposition, and this is followed by heat treatment etc. to grow the hollows 122 to form gaps (Japanese Patent O.P.I. Publication No. 110200/1987). Note that 124 is a protective layer.
However, the method of (1) above is faulty in that the process of forming the fine rugged pattern 91 on the support 92 is complicated and there is a limitation on fining the pattern 91, which in turn limits image sharpness.
The method of (2) requires a process of shock treatment, leading to an additional cost of production.
The methods (3) and (4) are both faulty in that uniformization of gap density on panels of large area is difficult, and a process of shock treatment is necessary as in the method of (2).